Experimental Studies on Locomotor Experience

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BCS-0002001PI: Joseph Campos Over the past several years, we have discovered a period of extraordinary psychological changes after the infant begins to crawl. These changes are very broad, and involve perception, spatial understanding, positive and negative emotions, and social interactions within the family. These discoveries have come about through the use of a variety of methods, including studies of early and late crawling infants, infants who use walker devices, infants with locomotor handicaps, and infants in different cultures. While yielding findings highly suggestive that locomotor experience in some way causes these changes, it remains possible that the onset of locomotion may serve merely as a maturational forecaster of psychological changes to come, and that there is no intrinsic causal link between locomotor experience and psychological development. The proposed studies are designed to clarify this state of affairs. Only a true experiment involving the random assignment of participants to conditions can ensure confident inference about causation. Consequently, we will conduct such an experimental investigation into the role of locomotor experience on psychological development. To carry out a true experiment, we have devised a Powered Mobility Device (PMD), a small electric-powered cart the movement of which can be controlled by a joystick. Prior studies have shown that prelocomotor infants can, in fact, learn to control such a PMD. Building on these findings, we will now randomly assign infants into conditions in which the infant can voluntarily control the PMD, or passively ride in the PMD in the same way as another matched infant. Funding from this grant will permit preliminary investigation of such an experimental manipulation. To assess outcomes related to PMD experience, we will assess the infants on two tests that have been shown to be robust consequences of locomotor experience in earlier studies. One of these outcomes will determine the extent of infant postural compensation to peripheral optic flow (i.e., visual proprioception), and the other will test wariness of heights (on the so-called "visual cliff"). Prior to initiating the outcome testing, we will conduct extensive pilot work using modifications of the visual proprioception and visual cliff tasks that are designed to increase the responsiveness of infants on both tests. In addition, we will conduct other pilot work to explore whether the control by the infant of the PMD will involve goal-directed action (i.e., voluntary stopping at a location where the mother can be found), and whether the infant can learn to steer the PMD around obstacles that prevent the infant from reaching a desired goal.This study has important implications for understanding the processes underlying developmental transitions in infancy. In addition, the research has implications for how self-produced experiences by a child may affect the course and organization of brain growth and development.